Merge branch 'for-3.10' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq

Pull workqueue updates from Tejun Heo:
 "A lot of activities on workqueue side this time.  The changes achieve
  the followings.

   - WQ_UNBOUND workqueues - the workqueues which are per-cpu - are
     updated to be able to interface with multiple backend worker pools.
     This involved a lot of churning but the end result seems actually
     neater as unbound workqueues are now a lot closer to per-cpu ones.

   - The ability to interface with multiple backend worker pools are
     used to implement unbound workqueues with custom attributes.
     Currently the supported attributes are the nice level and CPU
     affinity.  It may be expanded to include cgroup association in
     future.  The attributes can be specified either by calling
     apply_workqueue_attrs() or through /sys/bus/workqueue/WQ_NAME/* if
     the workqueue in question is exported through sysfs.

     The backend worker pools are keyed by the actual attributes and
     shared by any workqueues which share the same attributes.  When
     attributes of a workqueue are changed, the workqueue binds to the
     worker pool with the specified attributes while leaving the work
     items which are already executing in its previous worker pools
     alone.

     This allows converting custom worker pool implementations which
     want worker attribute tuning to use workqueues.  The writeback pool
     is already converted in block tree and there are a couple others
     are likely to follow including btrfs io workers.

   - WQ_UNBOUND's ability to bind to multiple worker pools is also used
     to make it NUMA-aware.  Because there's no association between work
     item issuer and the specific worker assigned to execute it, before
     this change, using unbound workqueue led to unnecessary cross-node
     bouncing and it couldn't be helped by autonuma as it requires tasks
     to have implicit node affinity and workers are assigned randomly.

     After these changes, an unbound workqueue now binds to multiple
     NUMA-affine worker pools so that queued work items are executed in
     the same node.  This is turned on by default but can be disabled
     system-wide or for individual workqueues.

     Crypto was requesting NUMA affinity as encrypting data across
     different nodes can contribute noticeable overhead and doing it
     per-cpu was too limiting for certain cases and IO throughput could
     be bottlenecked by one CPU being fully occupied while others have
     idle cycles.

  While the new features required a lot of changes including
  restructuring locking, it didn't complicate the execution paths much.
  The unbound workqueue handling is now closer to per-cpu ones and the
  new features are implemented by simply associating a workqueue with
  different sets of backend worker pools without changing queue,
  execution or flush paths.

  As such, even though the amount of change is very high, I feel
  relatively safe in that it isn't likely to cause subtle issues with
  basic correctness of work item execution and handling.  If something
  is wrong, it's likely to show up as being associated with worker pools
  with the wrong attributes or OOPS while workqueue attributes are being
  changed or during CPU hotplug.

  While this creates more backend worker pools, it doesn't add too many
  more workers unless, of course, there are many workqueues with unique
  combinations of attributes.  Assuming everything else is the same,
  NUMA awareness costs an extra worker pool per NUMA node with online
  CPUs.

  There are also a couple things which are being routed outside the
  workqueue tree.

   - block tree pulled in workqueue for-3.10 so that writeback worker
     pool can be converted to unbound workqueue with sysfs control
     exposed.  This simplifies the code, makes writeback workers
     NUMA-aware and allows tuning nice level and CPU affinity via sysfs.

   - The conversion to workqueue means that there's no 1:1 association
     between a specific worker, which makes writeback folks unhappy as
     they want to be able to tell which filesystem caused a problem from
     backtrace on systems with many filesystems mounted.  This is
     resolved by allowing work items to set debug info string which is
     printed when the task is dumped.  As this change involves unifying
     implementations of dump_stack() and friends in arch codes, it's
     being routed through Andrew's -mm tree."

* 'for-3.10' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq: (84 commits)
  workqueue: use kmem_cache_free() instead of kfree()
  workqueue: avoid false negative WARN_ON() in destroy_workqueue()
  workqueue: update sysfs interface to reflect NUMA awareness and a kernel param to disable NUMA affinity
  workqueue: implement NUMA affinity for unbound workqueues
  workqueue: introduce put_pwq_unlocked()
  workqueue: introduce numa_pwq_tbl_install()
  workqueue: use NUMA-aware allocation for pool_workqueues
  workqueue: break init_and_link_pwq() into two functions and introduce alloc_unbound_pwq()
  workqueue: map an unbound workqueues to multiple per-node pool_workqueues
  workqueue: move hot fields of workqueue_struct to the end
  workqueue: make workqueue->name[] fixed len
  workqueue: add workqueue->unbound_attrs
  workqueue: determine NUMA node of workers accourding to the allowed cpumask
  workqueue: drop 'H' from kworker names of unbound worker pools
  workqueue: add wq_numa_tbl_len and wq_numa_possible_cpumask[]
  workqueue: move pwq_pool_locking outside of get/put_unbound_pool()
  workqueue: fix memory leak in apply_workqueue_attrs()
  workqueue: fix unbound workqueue attrs hashing / comparison
  workqueue: fix race condition in unbound workqueue free path
  workqueue: remove pwq_lock which is no longer used
  ...

6 files changed, 1985 insertions, 883 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index dfaf50d4705e..1f628bc039f4 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2224,11 +2224,11 @@ retry_find_task:
 		tsk = tsk->group_leader;
 
 	/*
-	 * Workqueue threads may acquire PF_THREAD_BOUND and become
+	 * Workqueue threads may acquire PF_NO_SETAFFINITY and become
 	 * trapped in a cpuset, or RT worker may be born in a cgroup
 	 * with no rt_runtime allocated.  Just say no.
 	 */
-	if (tsk == kthreadd_task || (tsk->flags & PF_THREAD_BOUND)) {
+	if (tsk == kthreadd_task || (tsk->flags & PF_NO_SETAFFINITY)) {
 		ret = -EINVAL;
 		rcu_read_unlock();
 		goto out_unlock_cgroup;
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 334d983a36b2..027a6f65f2ad 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1388,16 +1388,16 @@ static int cpuset_can_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
 
 	cgroup_taskset_for_each(task, cgrp, tset) {
 		/*
-		 * Kthreads bound to specific cpus cannot be moved to a new
-		 * cpuset; we cannot change their cpu affinity and
-		 * isolating such threads by their set of allowed nodes is
-		 * unnecessary.  Thus, cpusets are not applicable for such
-		 * threads.  This prevents checking for success of
-		 * set_cpus_allowed_ptr() on all attached tasks before
-		 * cpus_allowed may be changed.
+		 * Kthreads which disallow setaffinity shouldn't be moved
+		 * to a new cpuset; we don't want to change their cpu
+		 * affinity and isolating such threads by their set of
+		 * allowed nodes is unnecessary.  Thus, cpusets are not
+		 * applicable for such threads.  This prevents checking for
+		 * success of set_cpus_allowed_ptr() on all attached tasks
+		 * before cpus_allowed may be changed.
 		 */
 		ret = -EINVAL;
-		if (task->flags & PF_THREAD_BOUND)
+		if (task->flags & PF_NO_SETAFFINITY)
 			goto out_unlock;
 		ret = security_task_setscheduler(task);
 		if (ret)
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 9b12d65186f7..16d8ddd268b1 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -278,7 +278,7 @@ static void __kthread_bind(struct task_struct *p, unsigned int cpu, long state)
 	}
 	/* It's safe because the task is inactive. */
 	do_set_cpus_allowed(p, cpumask_of(cpu));
-	p->flags |= PF_THREAD_BOUND;
+	p->flags |= PF_NO_SETAFFINITY;
 }
 
 /**
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 42053547e0f5..d8285eb0cde6 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4083,6 +4083,10 @@ long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
 	get_task_struct(p);
 	rcu_read_unlock();
 
+	if (p->flags & PF_NO_SETAFFINITY) {
+		retval = -EINVAL;
+		goto out_put_task;
+	}
 	if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
 		retval = -ENOMEM;
 		goto out_put_task;
@@ -4730,11 +4734,6 @@ int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask)
 		goto out;
 	}
 
-	if (unlikely((p->flags & PF_THREAD_BOUND) && p != current)) {
-		ret = -EINVAL;
-		goto out;
-	}
-
 	do_set_cpus_allowed(p, new_mask);
 
 	/* Can the task run on the task's current CPU? If so, we're done */
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index b48cd597145d..154aa12af48e 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -41,7 +41,11 @@
 #include <linux/debug_locks.h>
 #include <linux/lockdep.h>
 #include <linux/idr.h>
+#include <linux/jhash.h>
 #include <linux/hashtable.h>
+#include <linux/rculist.h>
+#include <linux/nodemask.h>
+#include <linux/moduleparam.h>
 
 #include "workqueue_internal.h"
 
@@ -58,12 +62,11 @@ enum {
 	 * %WORKER_UNBOUND set and concurrency management disabled, and may
 	 * be executing on any CPU.  The pool behaves as an unbound one.
 	 *
-	 * Note that DISASSOCIATED can be flipped only while holding
-	 * assoc_mutex to avoid changing binding state while
+	 * Note that DISASSOCIATED should be flipped only while holding
+	 * manager_mutex to avoid changing binding state while
 	 * create_worker() is in progress.
 	 */
 	POOL_MANAGE_WORKERS	= 1 << 0,	/* need to manage workers */
-	POOL_MANAGING_WORKERS   = 1 << 1,       /* managing workers */
 	POOL_DISASSOCIATED	= 1 << 2,	/* cpu can't serve workers */
 	POOL_FREEZING		= 1 << 3,	/* freeze in progress */
 
@@ -74,12 +77,14 @@ enum {
 	WORKER_PREP		= 1 << 3,	/* preparing to run works */
 	WORKER_CPU_INTENSIVE	= 1 << 6,	/* cpu intensive */
 	WORKER_UNBOUND		= 1 << 7,	/* worker is unbound */
+	WORKER_REBOUND		= 1 << 8,	/* worker was rebound */
 
-	WORKER_NOT_RUNNING	= WORKER_PREP | WORKER_UNBOUND |
-				  WORKER_CPU_INTENSIVE,
+	WORKER_NOT_RUNNING	= WORKER_PREP | WORKER_CPU_INTENSIVE |
+				  WORKER_UNBOUND | WORKER_REBOUND,
 
 	NR_STD_WORKER_POOLS	= 2,		/* # standard pools per cpu */
 
+	UNBOUND_POOL_HASH_ORDER	= 6,		/* hashed by pool->attrs */
 	BUSY_WORKER_HASH_ORDER	= 6,		/* 64 pointers */
 
 	MAX_IDLE_WORKERS_RATIO	= 4,		/* 1/4 of busy can be idle */
@@ -97,6 +102,8 @@ enum {
 	 */
 	RESCUER_NICE_LEVEL	= -20,
 	HIGHPRI_NICE_LEVEL	= -20,
+
+	WQ_NAME_LEN		= 24,
 };
 
 /*
@@ -115,16 +122,26 @@ enum {
  *    cpu or grabbing pool->lock is enough for read access.  If
  *    POOL_DISASSOCIATED is set, it's identical to L.
  *
- * F: wq->flush_mutex protected.
+ * MG: pool->manager_mutex and pool->lock protected.  Writes require both
+ *     locks.  Reads can happen under either lock.
+ *
+ * PL: wq_pool_mutex protected.
+ *
+ * PR: wq_pool_mutex protected for writes.  Sched-RCU protected for reads.
+ *
+ * WQ: wq->mutex protected.
  *
- * W: workqueue_lock protected.
+ * WR: wq->mutex protected for writes.  Sched-RCU protected for reads.
+ *
+ * MD: wq_mayday_lock protected.
  */
 
 /* struct worker is defined in workqueue_internal.h */
 
 struct worker_pool {
 	spinlock_t		lock;		/* the pool lock */
-	unsigned int		cpu;		/* I: the associated cpu */
+	int			cpu;		/* I: the associated cpu */
+	int			node;		/* I: the associated node ID */
 	int			id;		/* I: pool ID */
 	unsigned int		flags;		/* X: flags */
 
@@ -138,12 +155,18 @@ struct worker_pool {
 	struct timer_list	idle_timer;	/* L: worker idle timeout */
 	struct timer_list	mayday_timer;	/* L: SOS timer for workers */
 
-	/* workers are chained either in busy_hash or idle_list */
+	/* a workers is either on busy_hash or idle_list, or the manager */
 	DECLARE_HASHTABLE(busy_hash, BUSY_WORKER_HASH_ORDER);
 						/* L: hash of busy workers */
 
-	struct mutex		assoc_mutex;	/* protect POOL_DISASSOCIATED */
-	struct ida		worker_ida;	/* L: for worker IDs */
+	/* see manage_workers() for details on the two manager mutexes */
+	struct mutex		manager_arb;	/* manager arbitration */
+	struct mutex		manager_mutex;	/* manager exclusion */
+	struct idr		worker_idr;	/* MG: worker IDs and iteration */
+
+	struct workqueue_attrs	*attrs;		/* I: worker attributes */
+	struct hlist_node	hash_node;	/* PL: unbound_pool_hash node */
+	int			refcnt;		/* PL: refcnt for unbound pools */
 
 	/*
 	 * The current concurrency level.  As it's likely to be accessed
@@ -151,6 +174,12 @@ struct worker_pool {
 	 * cacheline.
 	 */
 	atomic_t		nr_running ____cacheline_aligned_in_smp;
+
+	/*
+	 * Destruction of pool is sched-RCU protected to allow dereferences
+	 * from get_work_pool().
+	 */
+	struct rcu_head		rcu;
 } ____cacheline_aligned_in_smp;
 
 /*
@@ -164,75 +193,107 @@ struct pool_workqueue {
 	struct workqueue_struct *wq;		/* I: the owning workqueue */
 	int			work_color;	/* L: current color */
 	int			flush_color;	/* L: flushing color */
+	int			refcnt;		/* L: reference count */
 	int			nr_in_flight[WORK_NR_COLORS];
 						/* L: nr of in_flight works */
 	int			nr_active;	/* L: nr of active works */
 	int			max_active;	/* L: max active works */
 	struct list_head	delayed_works;	/* L: delayed works */
-};
+	struct list_head	pwqs_node;	/* WR: node on wq->pwqs */
+	struct list_head	mayday_node;	/* MD: node on wq->maydays */
+
+	/*
+	 * Release of unbound pwq is punted to system_wq.  See put_pwq()
+	 * and pwq_unbound_release_workfn() for details.  pool_workqueue
+	 * itself is also sched-RCU protected so that the first pwq can be
+	 * determined without grabbing wq->mutex.
+	 */
+	struct work_struct	unbound_release_work;
+	struct rcu_head		rcu;
+} __aligned(1 << WORK_STRUCT_FLAG_BITS);
 
 /*
  * Structure used to wait for workqueue flush.
  */
 struct wq_flusher {
-	struct list_head	list;		/* F: list of flushers */
-	int			flush_color;	/* F: flush color waiting for */
+	struct list_head	list;		/* WQ: list of flushers */
+	int			flush_color;	/* WQ: flush color waiting for */
 	struct completion	done;		/* flush completion */
 };
 
-/*
- * All cpumasks are assumed to be always set on UP and thus can't be
- * used to determine whether there's something to be done.
- */
-#ifdef CONFIG_SMP
-typedef cpumask_var_t mayday_mask_t;
-#define mayday_test_and_set_cpu(cpu, mask)	\
-	cpumask_test_and_set_cpu((cpu), (mask))
-#define mayday_clear_cpu(cpu, mask)		cpumask_clear_cpu((cpu), (mask))
-#define for_each_mayday_cpu(cpu, mask)		for_each_cpu((cpu), (mask))
-#define alloc_mayday_mask(maskp, gfp)		zalloc_cpumask_var((maskp), (gfp))
-#define free_mayday_mask(mask)			free_cpumask_var((mask))
-#else
-typedef unsigned long mayday_mask_t;
-#define mayday_test_and_set_cpu(cpu, mask)	test_and_set_bit(0, &(mask))
-#define mayday_clear_cpu(cpu, mask)		clear_bit(0, &(mask))
-#define for_each_mayday_cpu(cpu, mask)		if ((cpu) = 0, (mask))
-#define alloc_mayday_mask(maskp, gfp)		true
-#define free_mayday_mask(mask)			do { } while (0)
-#endif
+struct wq_device;
 
 /*
- * The externally visible workqueue abstraction is an array of
- * per-CPU workqueues:
+ * The externally visible workqueue.  It relays the issued work items to
+ * the appropriate worker_pool through its pool_workqueues.
  */
 struct workqueue_struct {
-	unsigned int		flags;		/* W: WQ_* flags */
-	union {
-		struct pool_workqueue __percpu		*pcpu;
-		struct pool_workqueue			*single;
-		unsigned long				v;
-	} pool_wq;				/* I: pwq's */
-	struct list_head	list;		/* W: list of all workqueues */
-
-	struct mutex		flush_mutex;	/* protects wq flushing */
-	int			work_color;	/* F: current work color */
-	int			flush_color;	/* F: current flush color */
+	struct list_head	pwqs;		/* WR: all pwqs of this wq */
+	struct list_head	list;		/* PL: list of all workqueues */
+
+	struct mutex		mutex;		/* protects this wq */
+	int			work_color;	/* WQ: current work color */
+	int			flush_color;	/* WQ: current flush color */
 	atomic_t		nr_pwqs_to_flush; /* flush in progress */
-	struct wq_flusher	*first_flusher;	/* F: first flusher */
-	struct list_head	flusher_queue;	/* F: flush waiters */
-	struct list_head	flusher_overflow; /* F: flush overflow list */
+	struct wq_flusher	*first_flusher;	/* WQ: first flusher */
+	struct list_head	flusher_queue;	/* WQ: flush waiters */
+	struct list_head	flusher_overflow; /* WQ: flush overflow list */
 
-	mayday_mask_t		mayday_mask;	/* cpus requesting rescue */
+	struct list_head	maydays;	/* MD: pwqs requesting rescue */
 	struct worker		*rescuer;	/* I: rescue worker */
 
-	int			nr_drainers;	/* W: drain in progress */
-	int			saved_max_active; /* W: saved pwq max_active */
+	int			nr_drainers;	/* WQ: drain in progress */
+	int			saved_max_active; /* WQ: saved pwq max_active */
+
+	struct workqueue_attrs	*unbound_attrs;	/* WQ: only for unbound wqs */
+	struct pool_workqueue	*dfl_pwq;	/* WQ: only for unbound wqs */
+
+#ifdef CONFIG_SYSFS
+	struct wq_device	*wq_dev;	/* I: for sysfs interface */
+#endif
 #ifdef CONFIG_LOCKDEP
 	struct lockdep_map	lockdep_map;
 #endif
-	char			name[];		/* I: workqueue name */
+	char			name[WQ_NAME_LEN]; /* I: workqueue name */
+
+	/* hot fields used during command issue, aligned to cacheline */
+	unsigned int		flags ____cacheline_aligned; /* WQ: WQ_* flags */
+	struct pool_workqueue __percpu *cpu_pwqs; /* I: per-cpu pwqs */
+	struct pool_workqueue __rcu *numa_pwq_tbl[]; /* FR: unbound pwqs indexed by node */
 };
 
+static struct kmem_cache *pwq_cache;
+
+static int wq_numa_tbl_len;		/* highest possible NUMA node id + 1 */
+static cpumask_var_t *wq_numa_possible_cpumask;
+					/* possible CPUs of each node */
+
+static bool wq_disable_numa;
+module_param_named(disable_numa, wq_disable_numa, bool, 0444);
+
+static bool wq_numa_enabled;		/* unbound NUMA affinity enabled */
+
+/* buf for wq_update_unbound_numa_attrs(), protected by CPU hotplug exclusion */
+static struct workqueue_attrs *wq_update_unbound_numa_attrs_buf;
+
+static DEFINE_MUTEX(wq_pool_mutex);	/* protects pools and workqueues list */
+static DEFINE_SPINLOCK(wq_mayday_lock);	/* protects wq->maydays list */
+
+static LIST_HEAD(workqueues);		/* PL: list of all workqueues */
+static bool workqueue_freezing;		/* PL: have wqs started freezing? */
+
+/* the per-cpu worker pools */
+static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS],
+				     cpu_worker_pools);
+
+static DEFINE_IDR(worker_pool_idr);	/* PR: idr of all pools */
+
+/* PL: hash of all unbound pools keyed by pool->attrs */
+static DEFINE_HASHTABLE(unbound_pool_hash, UNBOUND_POOL_HASH_ORDER);
+
+/* I: attributes used when instantiating standard unbound pools on demand */
+static struct workqueue_attrs *unbound_std_wq_attrs[NR_STD_WORKER_POOLS];
+
 struct workqueue_struct *system_wq __read_mostly;
 EXPORT_SYMBOL_GPL(system_wq);
 struct workqueue_struct *system_highpri_wq __read_mostly;
@@ -244,64 +305,87 @@ EXPORT_SYMBOL_GPL(system_unbound_wq);
 struct workqueue_struct *system_freezable_wq __read_mostly;
 EXPORT_SYMBOL_GPL(system_freezable_wq);
 
+static int worker_thread(void *__worker);
+static void copy_workqueue_attrs(struct workqueue_attrs *to,
+				 const struct workqueue_attrs *from);
+
 #define CREATE_TRACE_POINTS
 #include <trace/events/workqueue.h>
 
-#define for_each_std_worker_pool(pool, cpu)				\
-	for ((pool) = &std_worker_pools(cpu)[0];			\
-	     (pool) < &std_worker_pools(cpu)[NR_STD_WORKER_POOLS]; (pool)++)
+#define assert_rcu_or_pool_mutex()					\
+	rcu_lockdep_assert(rcu_read_lock_sched_held() ||		\
+			   lockdep_is_held(&wq_pool_mutex),		\
+			   "sched RCU or wq_pool_mutex should be held")
 
-#define for_each_busy_worker(worker, i, pool)				\
-	hash_for_each(pool->busy_hash, i, worker, hentry)
+#define assert_rcu_or_wq_mutex(wq)					\
+	rcu_lockdep_assert(rcu_read_lock_sched_held() ||		\
+			   lockdep_is_held(&wq->mutex),			\
+			   "sched RCU or wq->mutex should be held")
 
-static inline int __next_wq_cpu(int cpu, const struct cpumask *mask,
-				unsigned int sw)
-{
-	if (cpu < nr_cpu_ids) {
-		if (sw & 1) {
-			cpu = cpumask_next(cpu, mask);
-			if (cpu < nr_cpu_ids)
-				return cpu;
-		}
-		if (sw & 2)
-			return WORK_CPU_UNBOUND;
-	}
-	return WORK_CPU_END;
-}
+#ifdef CONFIG_LOCKDEP
+#define assert_manager_or_pool_lock(pool)				\
+	WARN_ONCE(debug_locks &&					\
+		  !lockdep_is_held(&(pool)->manager_mutex) &&		\
+		  !lockdep_is_held(&(pool)->lock),			\
+		  "pool->manager_mutex or ->lock should be held")
+#else
+#define assert_manager_or_pool_lock(pool)	do { } while (0)
+#endif
 
-static inline int __next_pwq_cpu(int cpu, const struct cpumask *mask,
-				 struct workqueue_struct *wq)
-{
-	return __next_wq_cpu(cpu, mask, !(wq->flags & WQ_UNBOUND) ? 1 : 2);
-}
+#define for_each_cpu_worker_pool(pool, cpu)				\
+	for ((pool) = &per_cpu(cpu_worker_pools, cpu)[0];		\
+	     (pool) < &per_cpu(cpu_worker_pools, cpu)[NR_STD_WORKER_POOLS]; \
+	     (pool)++)
 
-/*
- * CPU iterators
+/**
+ * for_each_pool - iterate through all worker_pools in the system
+ * @pool: iteration cursor
+ * @pi: integer used for iteration
  *
- * An extra cpu number is defined using an invalid cpu number
- * (WORK_CPU_UNBOUND) to host workqueues which are not bound to any
- * specific CPU.  The following iterators are similar to for_each_*_cpu()
- * iterators but also considers the unbound CPU.
+ * This must be called either with wq_pool_mutex held or sched RCU read
+ * locked.  If the pool needs to be used beyond the locking in effect, the
+ * caller is responsible for guaranteeing that the pool stays online.
  *
- * for_each_wq_cpu()		: possible CPUs + WORK_CPU_UNBOUND
- * for_each_online_wq_cpu()	: online CPUs + WORK_CPU_UNBOUND
- * for_each_pwq_cpu()		: possible CPUs for bound workqueues,
- *				  WORK_CPU_UNBOUND for unbound workqueues
+ * The if/else clause exists only for the lockdep assertion and can be
+ * ignored.
  */
-#define for_each_wq_cpu(cpu)						\
-	for ((cpu) = __next_wq_cpu(-1, cpu_possible_mask, 3);		\
-	     (cpu) < WORK_CPU_END;					\
-	     (cpu) = __next_wq_cpu((cpu), cpu_possible_mask, 3))
+#define for_each_pool(pool, pi)						\
+	idr_for_each_entry(&worker_pool_idr, pool, pi)			\
+		if (({ assert_rcu_or_pool_mutex(); false; })) { }	\
+		else
 
-#define for_each_online_wq_cpu(cpu)					\
-	for ((cpu) = __next_wq_cpu(-1, cpu_online_mask, 3);		\
-	     (cpu) < WORK_CPU_END;					\
-	     (cpu) = __next_wq_cpu((cpu), cpu_online_mask, 3))
+/**
+ * for_each_pool_worker - iterate through all workers of a worker_pool
+ * @worker: iteration cursor
+ * @wi: integer used for iteration
+ * @pool: worker_pool to iterate workers of
+ *
+ * This must be called with either @pool->manager_mutex or ->lock held.
+ *
+ * The if/else clause exists only for the lockdep assertion and can be
+ * ignored.
+ */
+#define for_each_pool_worker(worker, wi, pool)				\
+	idr_for_each_entry(&(pool)->worker_idr, (worker), (wi))		\
+		if (({ assert_manager_or_pool_lock((pool)); false; })) { } \
+		else
 
-#define for_each_pwq_cpu(cpu, wq)					\
-	for ((cpu) = __next_pwq_cpu(-1, cpu_possible_mask, (wq));	\
-	     (cpu) < WORK_CPU_END;					\
-	     (cpu) = __next_pwq_cpu((cpu), cpu_possible_mask, (wq)))
+/**
+ * for_each_pwq - iterate through all pool_workqueues of the specified workqueue
+ * @pwq: iteration cursor
+ * @wq: the target workqueue
+ *
+ * This must be called either with wq->mutex held or sched RCU read locked.
+ * If the pwq needs to be used beyond the locking in effect, the caller is
+ * responsible for guaranteeing that the pwq stays online.
+ *
+ * The if/else clause exists only for the lockdep assertion and can be
+ * ignored.
+ */
+#define for_each_pwq(pwq, wq)						\
+	list_for_each_entry_rcu((pwq), &(wq)->pwqs, pwqs_node)		\
+		if (({ assert_rcu_or_wq_mutex(wq); false; })) { }	\
+		else
 
 #ifdef CONFIG_DEBUG_OBJECTS_WORK
 
@@ -419,77 +503,35 @@ static inline void debug_work_activate(struct work_struct *work) { }
 static inline void debug_work_deactivate(struct work_struct *work) { }
 #endif
 
-/* Serializes the accesses to the list of workqueues. */
-static DEFINE_SPINLOCK(workqueue_lock);
-static LIST_HEAD(workqueues);
-static bool workqueue_freezing;		/* W: have wqs started freezing? */
-
-/*
- * The CPU and unbound standard worker pools.  The unbound ones have
- * POOL_DISASSOCIATED set, and their workers have WORKER_UNBOUND set.
- */
-static DEFINE_PER_CPU_SHARED_ALIGNED(struct worker_pool [NR_STD_WORKER_POOLS],
-				     cpu_std_worker_pools);
-static struct worker_pool unbound_std_worker_pools[NR_STD_WORKER_POOLS];
-
-/* idr of all pools */
-static DEFINE_MUTEX(worker_pool_idr_mutex);
-static DEFINE_IDR(worker_pool_idr);
-
-static int worker_thread(void *__worker);
-
-static struct worker_pool *std_worker_pools(int cpu)
-{
-	if (cpu != WORK_CPU_UNBOUND)
-		return per_cpu(cpu_std_worker_pools, cpu);
-	else
-		return unbound_std_worker_pools;
-}
-
-static int std_worker_pool_pri(struct worker_pool *pool)
-{
-	return pool - std_worker_pools(pool->cpu);
-}
-
 /* allocate ID and assign it to @pool */
 static int worker_pool_assign_id(struct worker_pool *pool)
 {
 	int ret;
 
-	mutex_lock(&worker_pool_idr_mutex);
+	lockdep_assert_held(&wq_pool_mutex);
+
 	ret = idr_alloc(&worker_pool_idr, pool, 0, 0, GFP_KERNEL);
-	if (ret >= 0)
+	if (ret >= 0) {
 		pool->id = ret;
-	mutex_unlock(&worker_pool_idr_mutex);
-
-	return ret < 0 ? ret : 0;
+		return 0;
+	}
+	return ret;
 }
 
-/*
- * Lookup worker_pool by id.  The idr currently is built during boot and
- * never modified.  Don't worry about locking for now.
+/**
+ * unbound_pwq_by_node - return the unbound pool_workqueue for the given node
+ * @wq: the target workqueue
+ * @node: the node ID
+ *
+ * This must be called either with pwq_lock held or sched RCU read locked.
+ * If the pwq needs to be used beyond the locking in effect, the caller is
+ * responsible for guaranteeing that the pwq stays online.
  */
-static struct worker_pool *worker_pool_by_id(int pool_id)
+static struct pool_workqueue *unbound_pwq_by_node(struct workqueue_struct *wq,
+						  int node)
 {
-	return idr_find(&worker_pool_idr, pool_id);
-}
-
-static struct worker_pool *get_std_worker_pool(int cpu, bool highpri)
-{
-	struct worker_pool *pools = std_worker_pools(cpu);
-
-	return &pools[highpri];
-}
-
-static struct pool_workqueue *get_pwq(unsigned int cpu,
-				      struct workqueue_struct *wq)
-{
-	if (!(wq->flags & WQ_UNBOUND)) {
-		if (likely(cpu < nr_cpu_ids))
-			return per_cpu_ptr(wq->pool_wq.pcpu, cpu);
-	} else if (likely(cpu == WORK_CPU_UNBOUND))
-		return wq->pool_wq.single;
-	return NULL;
+	assert_rcu_or_wq_mutex(wq);
+	return rcu_dereference_raw(wq->numa_pwq_tbl[node]);
 }
 
 static unsigned int work_color_to_flags(int color)
@@ -531,7 +573,7 @@ static int work_next_color(int color)
 static inline void set_work_data(struct work_struct *work, unsigned long data,
 				 unsigned long flags)
 {
-	BUG_ON(!work_pending(work));
+	WARN_ON_ONCE(!work_pending(work));
 	atomic_long_set(&work->data, data | flags | work_static(work));
 }
 
@@ -583,13 +625,23 @@ static struct pool_workqueue *get_work_pwq(struct work_struct *work)
  * @work: the work item of interest
  *
  * Return the worker_pool @work was last associated with.  %NULL if none.
+ *
+ * Pools are created and destroyed under wq_pool_mutex, and allows read
+ * access under sched-RCU read lock.  As such, this function should be
+ * called under wq_pool_mutex or with preemption disabled.
+ *
+ * All fields of the returned pool are accessible as long as the above
+ * mentioned locking is in effect.  If the returned pool needs to be used
+ * beyond the critical section, the caller is responsible for ensuring the
+ * returned pool is and stays online.
  */
 static struct worker_pool *get_work_pool(struct work_struct *work)
 {
 	unsigned long data = atomic_long_read(&work->data);
-	struct worker_pool *pool;
 	int pool_id;
 
+	assert_rcu_or_pool_mutex();
+
 	if (data & WORK_STRUCT_PWQ)
 		return ((struct pool_workqueue *)
 			(data & WORK_STRUCT_WQ_DATA_MASK))->pool;
@@ -598,9 +650,7 @@ static struct worker_pool *get_work_pool(struct work_struct *work)
 	if (pool_id == WORK_OFFQ_POOL_NONE)
 		return NULL;
 
-	pool = worker_pool_by_id(pool_id);
-	WARN_ON_ONCE(!pool);
-	return pool;
+	return idr_find(&worker_pool_idr, pool_id);
 }
 
 /**
@@ -689,7 +739,7 @@ static bool need_to_manage_workers(struct worker_pool *pool)
 /* Do we have too many workers and should some go away? */
 static bool too_many_workers(struct worker_pool *pool)
 {
-	bool managing = pool->flags & POOL_MANAGING_WORKERS;
+	bool managing = mutex_is_locked(&pool->manager_arb);
 	int nr_idle = pool->nr_idle + managing; /* manager is considered idle */
 	int nr_busy = pool->nr_workers - nr_idle;
 
@@ -744,7 +794,7 @@ static void wake_up_worker(struct worker_pool *pool)
  * CONTEXT:
  * spin_lock_irq(rq->lock)
  */
-void wq_worker_waking_up(struct task_struct *task, unsigned int cpu)
+void wq_worker_waking_up(struct task_struct *task, int cpu)
 {
 	struct worker *worker = kthread_data(task);
 
@@ -769,8 +819,7 @@ void wq_worker_waking_up(struct task_struct *task, unsigned int cpu)
  * RETURNS:
  * Worker task on @cpu to wake up, %NULL if none.
  */
-struct task_struct *wq_worker_sleeping(struct task_struct *task,
-				       unsigned int cpu)
+struct task_struct *wq_worker_sleeping(struct task_struct *task, int cpu)
 {
 	struct worker *worker = kthread_data(task), *to_wakeup = NULL;
 	struct worker_pool *pool;
@@ -786,7 +835,8 @@ struct task_struct *wq_worker_sleeping(struct task_struct *task,
 	pool = worker->pool;
 
 	/* this can only happen on the local cpu */
-	BUG_ON(cpu != raw_smp_processor_id());
+	if (WARN_ON_ONCE(cpu != raw_smp_processor_id()))
+		return NULL;
 
 	/*
 	 * The counterpart of the following dec_and_test, implied mb,
@@ -891,13 +941,12 @@ static inline void worker_clr_flags(struct worker *worker, unsigned int flags)
  * recycled work item as currently executing and make it wait until the
  * current execution finishes, introducing an unwanted dependency.
  *
- * This function checks the work item address, work function and workqueue
- * to avoid false positives.  Note that this isn't complete as one may
- * construct a work function which can introduce dependency onto itself
- * through a recycled work item.  Well, if somebody wants to shoot oneself
- * in the foot that badly, there's only so much we can do, and if such
- * deadlock actually occurs, it should be easy to locate the culprit work
- * function.
+ * This function checks the work item address and work function to avoid
+ * false positives.  Note that this isn't complete as one may construct a
+ * work function which can introduce dependency onto itself through a
+ * recycled work item.  Well, if somebody wants to shoot oneself in the
+ * foot that badly, there's only so much we can do, and if such deadlock
+ * actually occurs, it should be easy to locate the culprit work function.
  *
  * CONTEXT:
  * spin_lock_irq(pool->lock).
@@ -961,6 +1010,64 @@ static void move_linked_works(struct work_struct *work, struct list_head *head,
 		*nextp = n;
 }
 
+/**
+ * get_pwq - get an extra reference on the specified pool_workqueue
+ * @pwq: pool_workqueue to get
+ *
+ * Obtain an extra reference on @pwq.  The caller should guarantee that
+ * @pwq has positive refcnt and be holding the matching pool->lock.
+ */
+static void get_pwq(struct pool_workqueue *pwq)
+{
+	lockdep_assert_held(&pwq->pool->lock);
+	WARN_ON_ONCE(pwq->refcnt <= 0);
+	pwq->refcnt++;
+}
+
+/**
+ * put_pwq - put a pool_workqueue reference
+ * @pwq: pool_workqueue to put
+ *
+ * Drop a reference of @pwq.  If its refcnt reaches zero, schedule its
+ * destruction.  The caller should be holding the matching pool->lock.
+ */
+static void put_pwq(struct pool_workqueue *pwq)
+{
+	lockdep_assert_held(&pwq->pool->lock);
+	if (likely(--pwq->refcnt))
+		return;
+	if (WARN_ON_ONCE(!(pwq->wq->flags & WQ_UNBOUND)))
+		return;
+	/*
+	 * @pwq can't be released under pool->lock, bounce to
+	 * pwq_unbound_release_workfn().  This never recurses on the same
+	 * pool->lock as this path is taken only for unbound workqueues and
+	 * the release work item is scheduled on a per-cpu workqueue.  To
+	 * avoid lockdep warning, unbound pool->locks are given lockdep
+	 * subclass of 1 in get_unbound_pool().
+	 */
+	schedule_work(&pwq->unbound_release_work);
+}
+
+/**
+ * put_pwq_unlocked - put_pwq() with surrounding pool lock/unlock
+ * @pwq: pool_workqueue to put (can be %NULL)
+ *
+ * put_pwq() with locking.  This function also allows %NULL @pwq.
+ */
+static void put_pwq_unlocked(struct pool_workqueue *pwq)
+{
+	if (pwq) {
+		/*
+		 * As both pwqs and pools are sched-RCU protected, the
+		 * following lock operations are safe.
+		 */
+		spin_lock_irq(&pwq->pool->lock);
+		put_pwq(pwq);
+		spin_unlock_irq(&pwq->pool->lock);
+	}
+}
+
 static void pwq_activate_delayed_work(struct work_struct *work)
 {
 	struct pool_workqueue *pwq = get_work_pwq(work);
@@ -992,9 +1099,9 @@ static void pwq_activate_first_delayed(struct pool_workqueue *pwq)
  */
 static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, int color)
 {
-	/* ignore uncolored works */
+	/* uncolored work items don't participate in flushing or nr_active */
 	if (color == WORK_NO_COLOR)
-		return;
+		goto out_put;
 
 	pwq->nr_in_flight[color]--;
 
@@ -1007,11 +1114,11 @@ static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, int color)
 
 	/* is flush in progress and are we at the flushing tip? */
 	if (likely(pwq->flush_color != color))
-		return;
+		goto out_put;
 
 	/* are there still in-flight works? */
 	if (pwq->nr_in_flight[color])
-		return;
+		goto out_put;
 
 	/* this pwq is done, clear flush_color */
 	pwq->flush_color = -1;
@@ -1022,6 +1129,8 @@ static void pwq_dec_nr_in_flight(struct pool_workqueue *pwq, int color)
 	 */
 	if (atomic_dec_and_test(&pwq->wq->nr_pwqs_to_flush))
 		complete(&pwq->wq->first_flusher->done);
+out_put:
+	put_pwq(pwq);
 }
 
 /**
@@ -1144,11 +1253,12 @@ static void insert_work(struct pool_workqueue *pwq, struct work_struct *work,
 	/* we own @work, set data and link */
 	set_work_pwq(work, pwq, extra_flags);
 	list_add_tail(&work->entry, head);
+	get_pwq(pwq);
 
 	/*
-	 * Ensure either worker_sched_deactivated() sees the above
-	 * list_add_tail() or we see zero nr_running to avoid workers
-	 * lying around lazily while there are works to be processed.
+	 * Ensure either wq_worker_sleeping() sees the above
+	 * list_add_tail() or we see zero nr_running to avoid workers lying
+	 * around lazily while there are works to be processed.
 	 */
 	smp_mb();
 
@@ -1172,10 +1282,11 @@ static bool is_chained_work(struct workqueue_struct *wq)
 	return worker && worker->current_pwq->wq == wq;
 }
 
-static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
+static void __queue_work(int cpu, struct workqueue_struct *wq,
 			 struct work_struct *work)
 {
 	struct pool_workqueue *pwq;
+	struct worker_pool *last_pool;
 	struct list_head *worklist;
 	unsigned int work_flags;
 	unsigned int req_cpu = cpu;
@@ -1191,48 +1302,62 @@ static void __queue_work(unsigned int cpu, struct workqueue_struct *wq,
 	debug_work_activate(work);
 
 	/* if dying, only works from the same workqueue are allowed */
-	if (unlikely(wq->flags & WQ_DRAINING) &&
+	if (unlikely(wq->flags & __WQ_DRAINING) &&
 	    WARN_ON_ONCE(!is_chained_work(wq)))
 		return;
+retry:
+	if (req_cpu == WORK_CPU_UNBOUND)
+		cpu = raw_smp_processor_id();
 
-	/* determine the pwq to use */
-	if (!(wq->flags & WQ_UNBOUND)) {
-		struct worker_pool *last_pool;
-
-		if (cpu == WORK_CPU_UNBOUND)
-			cpu = raw_smp_processor_id();
-
-		/*
-		 * It's multi cpu.  If @work was previously on a different
-		 * cpu, it might still be running there, in which case the
-		 * work needs to be queued on that cpu to guarantee
-		 * non-reentrancy.
-		 */
-		pwq = get_pwq(cpu, wq);
-		last_pool = get_work_pool(work);
+	/* pwq which will be used unless @work is executing elsewhere */
+	if (!(wq->flags & WQ_UNBOUND))
+		pwq = per_cpu_ptr(wq->cpu_pwqs, cpu);
+	else
+		pwq = unbound_pwq_by_node(wq, cpu_to_node(cpu));
 
-		if (last_pool && last_pool != pwq->pool) {
-			struct worker *worker;
+	/*
+	 * If @work was previously on a different pool, it might still be
+	 * running there, in which case the work needs to be queued on that
+	 * pool to guarantee non-reentrancy.
+	 */
+	last_pool = get_work_pool(work);
+	if (last_pool && last_pool != pwq->pool) {
+		struct worker *worker;